Gold nanoclusters (GNCs) have received been considered as potential building blocks for a variety of nanoscale applications, including chemical sensing, electronics, optics, and biology. A scalable method for isolating significant quantities of GNCs with a known number of DNA strands per GNC would be useful in nanoscale applications dependent on using DNA molecular recognition in patterned self-assembly scemes, as DNA, with its highly specific base-pairing is attractive as the basis of self-assembly of nanoclusters. Earlier work demonstrated the feasibility of this approach using GNCs coupled with multiple oligonucleotides; but to go beyond these assemblies, and for diagnostics based on the quantification of hybridization events, it is essential to work with GNCs bearing one and only one oligonucleotide strand.
Methods for creating singly-attached nanoclusters have been developed, see Mirkin, et al. J. Nature 1996, 382, 607-609 and Alivisatos, et al, Nature 1996, 382, 609-611. However, the methods of Alivaisatos and Mirkin used gold nanoclusters that were stabilized by citrate, by phosphine or by thiolated DNA, which are charged, which can lead to non-specific interactions, either attractive or repulsive, particularly at low ionic strength. Additionally, these methods are appear to be limited to ssDNA tags of at least 50 bases long, which could create an imprecision in the ability to position small clusters by a templating strategy.
Therefore, there is a need in the art for a method for creating singly-attached nanoclusters that are not stabilized by citrate, phosphine or by thiolated DNAs. Additionally, there is a need in the art for a method for creating singly-attached nanoclusters are less than 50 bases long, allowing for the ability to position the cluster via a templating strategy.
These and other objectives are achieved by a method that utilizes a neutral cluster and allow for the synthesis and isolation of singly-attached clusters with ssDNA as short as 10-15 bases.